1. Field of the Invention
The invention generally relates to capacitive switches, and more particularly to a switch circuit arrangement having a flexible capacitor for use in a steering wheel application.
2. Background Description
An automobile horn has been traditionally used as a safety mechanism. A driver may use his horn to alert animals, pedestrians, and even other drivers as to the presence of the automobile. Given the necessity for a driver to be able to quickly activate a horn, a horn activation switch has been historically built into some portion of the steering wheel such as a touch bar, a touch pad or in the hub of the steering wheel. A relatively large area has been provided for use in activating the horn switch to make it easy to quickly activate the horn.
In response to the advent of driver's side airbags installed in steering wheel hubs, the hub integrated horn switch has become rare or the size of the horn switch has been greatly reduced. Driver's side airbags have effectively displaced horn switches from the steering wheel hub. Horn switches for many automobiles with air bags are mounted in spokes of the steering wheel or on the periphery of the hub. The present placement of horn switches often leaves drivers searching for the switches, many times finding switches only after danger has passed.
The present problems of horn switch placement have been recognized, and some manufacturers are implementing horn activation switches that are optimally mounted in the hubs of steering wheels. However, the driver's side airbag presents various problems in implementing a workable and cost-effective solution. One problem is that current single switch designs do not work reliably in the variety of steering wheels available from the major car manufacturers. It is difficult to adjust each design to accommodate a desired force for actuating the switch.
Generally, the switch is disposed between the airbag and the hub cover. The force required to actuate the switch may vary according to how the airbag is folded, the type of material used for the hub cover, and the geometry of the hub cover. Thus, a custom design may be required for different styles of steering wheels, and there may even be variations between instances of the same type of steering wheel. Additional problems may arise from differences in temperature and air pressure. The net result is increased manufacturing costs.
Therefore, it would be desirable to have a switch that overcomes the above stated problems.